Field of the Invention
The present invention relates to a technique for coding moving images (video) for the compression of moving images (video), and more particularly, to a technique for controlling the code amount in the compression of moving images (video).
Description of the Background Art
Techniques for compressing moving images (video) may include predicting the amount of code to be generated and controlling the bit rate (controlling the code amount) appropriately.
With a technique described in Patent Literature 1 (Japanese Patent No. 5251774), for example, a pre-encoder and an intra pre-encoder first perform an encoding process on a moving image (video) and obtain the amount of code generated through the encoding process before a main encoder actually compresses the moving image (video). With the technique described in Patent Literature 1, a code amount controller determines a quantization parameter value based on the code amount generated through the encoding process performed by the pre-encoder and the intra pre-encoder. The main encoder then performs a compression process (an actual encoding process) on the moving image (video) by using the quantization parameter value determined by the code amount controller.
In this manner, the technique described in Patent Literature 1 allows highly precise prediction of the code amount to be generated by the moving image (video) compression process (actual encoding process) based on the code amount generated through the encoding process performed by the pre-encoder and the intra pre-encoder. With the technique described in Patent Literature 1, the quantization parameter value is determined based on the precisely predicted code amount to be generated, and the main encoder performs the moving image (video) compression process (actual encoding process) by using the quantization parameter value. The technique described in Patent Literature 1 enables appropriate bit rate control (code amount control).
However, the moving image compression process performed on video containing much noise (video having a poor signal-to-noise or S/N ratio) with the technique in Patent Literature 1 may yield a large code amount to be generated, disabling appropriate bit rate control (code amount control). Noise contained in video typically has low correlations in both temporal or spatial directions. Thus, the moving image compression process performed on the video containing much noise may fail to increase the compression ratio. The pre encoding process with the technique of Patent Literature 1 may fail to achieve efficient moving image compression for video containing much noise (video having a poor S/N ratio).
In view of the above problems, it is an object of the present invention to provide a moving image coding apparatus, a moving image coding method, a storage medium, and an integrated circuit that allow efficient moving image compression of video containing much noise (video having a poor S/N ratio) and enable appropriate bit rate control (code amount control).